In the flow control application, for example, oil/gas production process switching, pipeline shut-off, metering, pressure regulation, molecular sieve switching, compressor inlet/outlet, hydrogen application in oil refining process, air separation of synthetic ammonia equipment, and the like, which require frequent operation and have strict requirements on flow on-off control and closing tightness, it is desired that valves produce a pressure drop as small as possible and can provide a forced torque seal without the influence of the pressure of fluid within the pipeline. Mechanical energized sealing ball valves are recognized as an ideal solution.
However, for the conventional rising stem mechanical energized sealing ball valve, although there is no contact or friction between the ball and the seat during most of the opening/closing stroke, sliding friction exists between the ball and seat sealing area during the final ball-seat engagement stage. Thus, valve operation is not a true friction-free rotation, and the ball against seat sealing relies on the stem wedging against ball, with ball being held by lower trunnion. As a result the movement is unsteady and susceptible to the influence of tolerance of the relative position of the seat and the lower trunnion. Additionally, the valve stem portion and its assembly have a complicated structure and require the combination of linear movement and rotation movement during the opening/closing process. The requirement for machining precision is strict, the risk of valve stem leakage is high, and the time of opening/closing operation is too long. The following six documents of mechanical energized sealing ball valve are found by SIPO patent inquiry:
Publication No. CN104295764A, Application No. 2014105008955: Disclosed is a valve that opens or close using a valve stem and a ball in eccentric arrangement and synchronous rotation. The design is essentially a modification of eccentric butterfly valve, in which a relative sliding friction between seat and ball sealing surface is produced due to a large angular stroke vector existing during the final siting stage of the ball and seat. Thus, it is not a true friction-free rotation, as the closing operation is an angular stroke, and the resulting normal component of force between the ball and the seat is not large, which may impact the sealing reliability and actual service life.
Publication No. CN103727260A, Application No. 2014100163761: Disclosed is a ball valve, in particular a mechanical energized sealing ball valve, comprising a valve body, a secondary valve body, a ball, a seat, and a secondary valve body fluid port, and a stud-nut-driving-type mechanical energized sealing device disposed on the shell of the secondary valve body fluid port. The worm wheel and the driving stud are coupled via a flat key, when the driving stud makes a rotational movement, the axial sliding key groove of the driven nut fits the driving stud in a rotating manner, enabling an axial linear movement along the guide key on the secondary valve body fluid port. As a result, a desired sealing specific pressure is generated between the seat and the ball within the valve cavity by the pressure generated outside the body through a pressure transfer system, thereby low-torque opening/closing and mechanical energized sealing can be achieved, and the interlinked actuation of the stud-nut energized sealing device and the electric actuator during opening/closing and sealing process are completed through an automatic control system. The design applies two operating mechanisms, one of them operates the ball to rotate 90 degrees, and the other operates the said secondary valve body for driving the seat to sit against ball. The design has many potential leakage paths, complicated structure and bulky size, and is not able to meet standard valve face-to-face dimensions.
Publication No. CN103527809A, Application No. 2013105342621: Disclosed is a valve comprising a valve body, a valve bonnet, a valve stem, a wedged plug and sealing members, characterized in that the top of the valve body is connected with the valve bonnet, the valve stem is vertically mounted in the center of the top of the valve body through a support, the wedged plug in the cavity of the valve body is fixed at the bottom of the valve stem by a pin through a hole in the center of the valve bonnet to synchronize the movement of the valve stem and the wedged plug, that is, rotating and raising aligned to a fixed axis. A fixed shaft is perpendicularly disposed in the bottom center of the cavity, the fixed shaft is matched with a hole in the bottom center of the wedged plug, the valve sealing members are fixed at the two sides of the bottom of the cavity through T-shaped grooves, valve sealing member stops are disposed on the top of the valve sealing member and on the inner walls of the two sides of the cavity, and the valve sealing member stops on the two sides are firmly connected with the two side walls of the wedged plug. The design is actually a mechanical energized plug valve (also known as DBB plug valve in the industry), although the valve can achieve mechanical energized sealing in a closed position, owing to the sliding-type sealing member configuration, the valve sealing member to be influenced by the turbulence when the valve is in the open position. At present, the design is used for applications under low pressure liquid working conditions only.
Publication No. CN102979929A, Application No. 2012105315085: Disclosed is a valve comprising a ball, a seat and a sealing ring seat disposed between the ball and the seat to perform the sealing, and a hydraulic device for pushing the sealing ring seat in the axial direction of the sealing ring seat, the hydraulic device being disposed between the seat and the sealing ring seat. The design realizes a forced seal by applying a pressure to the seal ring between the seat and the ball by using a set of hydraulic system, but the hydraulic leakage and complicated structure of the valve may affect the sealing reliability and service life of the valve.
Publication No. CN105370909A, Application No. 2014104406033: Disclosed is an opening/closing part having two eccentric spherical members. Such eccentric structure allows each of the two eccentric spherical surfaces to make a movement in the axial direction of the downstream seat and the upstream seat when the valve stem drives the opening/closing part to make a rotational movement, resulting in the effect of compressing or releasing the seat, thereby realizing the forced seal of the opening/closing part relative to the downstream seat and the upstream seat in a particular valve position. The valve of the design may be influenced by turbulence in the opening position, the two eccentric spherical members may be damaged by turbulence vibration, which affects the reliability and service life of the valve.
Publication No. CN104132157A, Application No. 2013101575904: Disclosed is a forced seal valve based on modular design and angular stroke operation, mainly comprising a valve body, an opening/closing part, a valve bonnet, a valve stem, a seat, a flow guide barrel, a seat support plate, a flow guide barrel support plate, an operating mechanism and a drainage valve. The opening/closing part is arranged between the seat and the flow guide barrel, by adjusting the relative position of sphere center and radii of the convex spherical surface and center of the concave spherical surface, the thicknesses of individual portions of the opening/closing part can be adjusted to adjust the sealing specific pressure between the opening/closing part and the seat when the valve is located in different valve positions, so that the valve realizes a forced seal in a certain valve position. Accordingly, the design is not a mechanical energized sealing ball valve in a whole sense.